The Other Side of the Integration Coin

Rich Q raised an interesting point in his comment, "Analog front ends," in response to my post, Superiority of Analog Integration Depends on Application. His question about AFEs (analog front ends) suggests an issue that design engineers always face when considering alternative product-design implementations: Is it better to take advantage of a highly integrated functional block or take on the additional design-cycle time and potential risk of a less integrated but more customizable design? The former locks your productís performance to an IC vendor's parametric choices and priorities but brings benefits in both time to market and design risk.

Engineering combines the art of balancing opposing forces, behaviors, and requirements with the science of fixing a given balance reliably and reproducibly through mass-manufacturing processes. In the current case, the trait opposing integration is segmentation: A decision about one is a commitment to the other.

Although it may seem to be an issue peculiar to IC technologies, this need to balance integration and segmentation predates monolithic circuits. Indeed, the concept dates back to the earliest complex electronic systems (if for no other reason than it allows designers to abstract a system as a collection of interconnected but otherwise approximately orthogonal functions).

So, at base level, segmentation can serve as an organizing principal allowing designers to manage project complexity and take advantage of a design teamís collective skill set and of vendorsí relevant technologies. But segmentation decisions do not only affect the design process. There are, for example, considerations for the competitive analysis designers and marketers must execute to justify a new-product development program before it starts: Market demand for parametric performance, cost, size, and power dissipation combine with time-to-market pressures and in-house expertise to inform make-or-buy decisions for various functional blocks.

In extremis, we have SOCs (systems on chip) -- an unfortunate marketing designation that always overstates the fact in an attempt to denote the current state-of-the-art in integration for a given application. These devices can subsume whole sections of a productís block diagram and can represent excellent value if and only if it leaves sufficient opportunity for the product developers to add differentiating value thatís meaningful to the marketplace.

And that, to my sensibilities, is where consideration of integration and segmentation begin: with an assessment of a product-development teamís value add in the context of market demands. After that the goal is often finding a balance in which highly integrated functions serve as problem-solving resources without their very solid-stateness imposing a brittleness on a design.

Yes, there are indeed three terminal ICs. Examples that come most readily to mind are three-terminal voltage references such as those exploiting the Brokaw Bandgap topology and three-terminal regulators.

But, beyond their abilities to invoke nostalgic sighs, those devices were quite distinct from other three terminal devices, such as discrete bipolar or MOS transistors, because of that barrier of abstraction thing I mentioned. That's a high-value attribute and, I'm thinking more and more, a compelling differentiating attribute.

In my book, neither op amps nor converters are discrete devices. Op amps may be small enough and cheap enough to sprinkle like pepper, but that doesn't change their nature.

Vendors design, verify, fabricate, and package these devices as they do more complex ICs. In that regard, they are subject to the same kinds of challenges and benefit from the same kinds of advancements as do more complex analog and mixed-signal blocks.

Beyond that, I think we make an important distinction between discrete components and integrated devices: Integrated devices provide barriers of abstraction that relieve designers from a great deal of technical detail compared to discrete designs. This changes the way we design with integrated functional blocks, be they as conceptually simple as an op amp or as complex as as a complete AFE.

With all this integration on ICs going on, dos it change what we call a "discrete" component? I remember in college I had a required take-home exam in my senior year. You had to pass to graduate. The design problem was written "using discrete components." Even then, we students asked if op amps were considered discrete components. The answer was the "discrete" meant no op amps, aonly transistors and diodes.

Is that different today? Would you consider an op amp as an integrated device or is it now so basic as to be considered more or less a transistor? Could ADCs and DACs even be considered discrete components.?

BTW, the requirement for this take-home "competency exam" was dropped several years after I was required to take it. I think that was a wise decision on the part of the school. Some who went through it considered it a rite of passage and that the school was making it easier to graduate. But in truth, just because you can pass an exam and get up in front of three professors to defend your design dosn't mean you'll be a competent engineer.

I don't know about the current curriculum, but when I was pursuing my engineering degree (@# years ago), game theory was not on the menu for EE students. Neither was project management or engineering risk assessment. Those "business of engineering" issues were left to one's first employer to teach. In retrospect, I think university engineering programs would benefit by including these issues in a coordinated set of lab courses if they don't already.

Fortunately, my summer interning job included what might be called Engineering Pragmatics 101 in the form of a generous and personable, but strict, supervisor.

Yes, this is an example of a broad range of complex analog and mixed-signal ICs for which the design team must have carefully considered issues of segmentation to appeal to as broad a range of customers as possible. I think medical-electronic AFEs are often prime examples because the required functionality for various devices tend to be both well defined and reasonably constrained. Another application example is communication PHYs (physical-layer ICs).

There are painful exceptions, but my experience has been that complex analog and mixed-signal devices offered as catalog parts typically come with a reasonable complement of documentation (though often distributed amongst several items such as data sheets, application notes, and the like). Remember it's in the manufacturer's best interest to ensure that the available documentation is sufficient to make users successful with minimum fuss and futzing because the alternatives--shipping an application engineer with every device or losing the customer to a competitor--are both far more expensive than generating sufficient documentation in the first place.

That said, devices that start out in life as CSICs (customer-specific integrated circuits) migrate to the catelog after an excusivity period elapses, and the vendor must re-evaluate the quality and completeness of its documentation in advance of releasing the part to the catalog. Suffice it to say, some vendors are more practiced in this regard than others.

Of course circuit and system designers have a responsibility to review the documentation vendors make available. I don't know what the track record is for this activity, but I note that RTFM (read the manual) is an acronym that dates back at least three decadespossibly twice thatand has probably survived for good reason.

Hi Joshua--I liked your thoughts on the tradeoffs. It occured to me you could write this down in standard game theory notation and solve it for equilibrium. What I would expect is happening are a lot of non-equilibrium choices where things like lack of complete information, over or under-estimating risk of either solution, pressure from a boss or colleague to go with one solution, vendor concessions on price, etc. create anomalies. Oh, the life of a design engineer.

@WKetel--There are off the shelf AFEs which if used might be considered a component, and if you then look at the total risk as a probability function, might lower the expected value of a stock-out. These would be previously characterized, already in production parts, not new custom designed parts. An example (I picked randomly) might be this TI front end:

One trhing that some of those organizations producing the very application specific chips may not have considered is the possibility that others might possibly use the device if an adequate amount of information about it was available. Of course there may be some sort of proprietary agreement in place about the device that would prevent marketing that device to others.

As the engineer responsible for designing a variety of systems for much smaller companies over the years, I can point out that on the opposite side, there are some very big advantages to using only those chips listed in the "commodity" catagory. The very first, and very big, benefit is part availability. When some manufacturer has a production quality or yield problem the alternate source is a lifesaver, even if the price is not quite as good. That saved me once on the '4038 one-shot, as one producers process somehow set the trigger threshold to a different piont. An alternate supplier's part still functioned as intended. So while it may be beneficial to put all of the system functions in one single sourced custom chip, it may be much wiser to use a set of the more common devices. And one other benefit, which is only to the purchaser of the product, is that it becomes possible to repair that product, since replacement parts are actually available. I have never been able to purchase a replacement for any of those custom chips, which has been a source of irritation on several occasions.